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<title>Explicit Register Variables (Using the GNU Compiler Collection (GCC))</title>

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<h4 class="subsection" id="Variables-in-Specified-Registers"><span>6.47.5 Variables in Specified Registers<a class="copiable-link" href="#Variables-in-Specified-Registers"> &para;</a></span></h4>
<a class="anchor" id="Explicit-Reg-Vars"></a><a class="index-entry-id" id="index-explicit-register-variables"></a>
<a class="index-entry-id" id="index-variables-in-specified-registers"></a>
<a class="index-entry-id" id="index-specified-registers"></a>

<p>GNU C allows you to associate specific hardware registers with C 
variables.  In almost all cases, allowing the compiler to assign
registers produces the best code.  However under certain unusual
circumstances, more precise control over the variable storage is 
required.
</p>
<p>Both global and local variables can be associated with a register.  The
consequences of performing this association are very different between
the two, as explained in the sections below.
</p>

<ul class="mini-toc">
<li><a href="Global-Register-Variables.html" accesskey="1">Defining Global Register Variables</a></li>
<li><a href="Local-Register-Variables.html" accesskey="2">Specifying Registers for Local Variables</a></li>
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